Inchgarvie’s fortifications pre-date the modern period. In the days when boats were the only way to cross the Firth of Forth, the island was on the main route between North Queensferry in Fife and South Queensferry in Lothian. This made it strategically important. Although now uninhabited, Inchgarvie has been inhabited throughout various periods of history. The first recorded time was in the late 15th century.

Like nearby Inchmickery, its profile and colour makes it look like a battleship from a distance, and it was used for gun placements during the world wars.

Contents

Records of Danish attacks on nearby islands, particularly Inchcolm as well as Fife and Lothian may mean that it was used in some capacity by them.

The island was licensed by King James IV to John Dundas of Dundas[note 1] with the power to build a fort on 20 March 1491.[4][5] John Dundas did not build the castle, and James IV himself ordered a strong tower to be built in 1513.[5]

On 8 March 1514 Margaret, the widow of William Dundas of Dundas, undertook to manage the completion of the fortress that James IV and her father-in-law had begun building on her island.[6] From 23 December 1514, Charles Dennison, Captain of Inchgarvie managed and fed a large royal construction team. The master mason was John of Cumbernauld, with his "servitor" John Strathauchin, who directed eight other masons and ten labourers. Margaret, Lady of Dundas gave them two boats. Two 'serpentine' guns and guns from Colstone were placed on the island after a visit by artillery experts in July 1515, and the island was equipped with a "blawing horne." There was also a chapel.[7]

Between 1519 and 1671, the castle was used as a prison, and in 1580 Inchkeith and Inchgarvie were made a place of exile for the plague-stricken by order of the Privy Council.[9] On 6 September 1627, the Laird of Dundas was invited to meet the Privy Council at South Queensferry and discuss building a modern fort on the island.[10] Like Inchkeith, Inchgarvie had a quarantine hospital, and a prison. Oliver Cromwell had this demolished.

In 1707 the island is known to have been rented to Archibald Primrose, 1st Earl of Rosebery. In 1779, however, the island's fortifications were renewed once more, in response to the threat posed by John Paul Jones, American Naval Commander, who harassed British ships from a base in the Forth.[11] These fortifications were never used in anger.

During the Napoleonic period, the threat from the sea meant gun batteries were created in 1806.[12]

In 1878 the foundations for Thomas Bouch's Forth Bridge were laid on Inchgarvie (and their bricks remain), but after the Tay Bridge Disaster, these plans were abandoned, and the island languished until the west end of the island was extended with a pier, and used as the foundation for one of the Forth Bridge'scantilevers. The island, due to its proximity to the bridge, was also used as a construction office for the bridge, as well as accommodation for its workers within the re-roofed castle buildings. Some of the stone from the former castle was used to help build the caissons of the Forth Bridge.